微电场辅助膜蒸馏工艺中静电作用对膜污染的调控机制研究

The membrane fouling or wetting caused by organic solutes restricts the application of membrane distillation (MD) in the field of wastewater treatment. Hydrophobic interactions and electrostatic interactions between membrane materials and organic foulants together regulate membrane fouling behavior, but the latter's contribution has been eclipsed, not receiving sufficient attention. Under the influence of the membrane hydrophobicity and the solution ionic strength, the charge strength of the membrane material may have to exceed a certain threshold to significantly regulate membrane fouling behavior given an electrostatic interaction between membrane and foulant. To further testify the above assumption, using oil-in-water emulsions of different charge as organic foulants, conductive membranes in an electrical field-assisted MD process, with independent control of its charge property and hydrophobicity, this project explores the effect and regularity of membrane charge property (polarity and strength) to control membrane fouling behavior; and further simulates the interfacial interaction between membrane and foulant based on XDLVO model, in order to explain the membrane fouling behavior under the interference of membrane hydrophobicity and solution ionic strength, as well as the mechanism behind, such that to establish an relationship modelling the foulant behavior at the response of membrane charge. The results of this project are of great significance to the mechanism of membrane fouling prevention and control, and provide a scientific basis for the preparation of new anti-fouling materials and the development of anti-fouling technology originating of electrostatic interaction in the future membrane technology.

膜蒸馏工艺在污水处理领域的应用严重受制于低表面能有机溶质所引起的膜污染（润湿）。在膜材料与污染物的作用界面上，亲疏水作用和静电作用共同调控着膜污染；但静电作用的贡献可能受到掩蔽，尚未引起足够关注。在膜材料的亲疏水性与溶液离子强度复合影响下，膜材料的荷电性可能需超过某临界强度才能显著发挥静电作用对膜污染的调控效果。为验证该假说，本项目以不同荷电性的水包油乳液为污染物、以导电型膜蒸馏材料为研究对象，采用微电场辅助下调控膜材料荷电性及其亲疏水性的方法，探索材料荷电性（荷电强度与极性）调控膜污染行为的效果与规律；并进一步基于XDLVO模型模拟膜与污染物的界面作用能，解析上述复合因素影响下膜污染的演变规律，阐明静电作用对膜污染的调控机制，建立膜污染对膜材料荷电性的响应规律模型。本项目成果对膜污染的防治机制具有重要意义，为未来膜工艺中新型抗污材料的制备及静电抗污技术的研发提供科学依据。

膜蒸馏（MD）是一种可利用余热或光热自驱动、高效截留污染物或浓缩污水、选择性透过水蒸气的绿色膜法水处理技术。膜材料与污染物在微观界面上的静电相互作用会影响透气膜的污染（润湿）演变，是除人们已熟知的亲疏水相互作用之外，潜在影响MD工艺应用推广前景的突破点之一。研究针对膜蒸馏工艺中静电作用调控膜污染行为的作用规律与机制不明的问题，以厘清静电作用控污潜能为目标，在具体解析不同荷电性水包油乳液（模式污染物）在导电膜蒸馏材料界面的过滤行为（污染表现）的基础上，提出了微电场辅助下独立调控膜材料荷电性及其亲疏水性的方法，探索了膜材料荷电性（荷电强度与极性）调控膜污染的效果与规律；重点解析了污染物与疏水透气膜互作体系中浸润性与荷电性的交互影响，阐明了静电作用对膜污染的调控机制，揭示出静电抗污技术在疏水透气膜领域的应用价值。.结果表明，以碳纳米管为导电材料、聚乙烯醇等为亲水材料、全氟十二烷基三乙氧基硅烷为疏水材料，通过界面负载与微电场辅助，可有效实现膜界面浸润性与荷电性的独立调控，污染实验验证了二者对膜污染的关键影响；在膜-污染物多元复配系统中，不同浸润性条件下静电作用对膜污染的调控规律并非线性；进一步分析发现膜界面浸润性对疏水膜污染的影响权重高达50%，膜界面电荷性对疏水膜污染的影响权重达到36%，静电作用调控疏水膜污染的作用效果不可忽略。上述成果为新一代膜材料与技术革新、膜污染防治提供了理论基础。